Within the context of clinical trials, the section evaluates methodological issues relevant to both research and treatment, such as monitoring drug use. In the past year, data from two contingency management trials, targeting opiate or cocaine use, were used to investigate whether noncontingent vouchers inadvertently reinforce drug use. The control group in each trial received noncontingent vouchers matched in value and frequency to those received by experimental groups, but independent of urinalysis. Vouchers were offered thrice weekly for 8 weeks (opiates) or 12 weeks (cocaine). Both dose-response and temporal associations of noncontingent voucher receipt with drug-positive urines were assessed. Drug use was unrelated to frequency of noncontingent voucher delivery, and noncontingent voucher receipt when drug-positive was unassociated with risk of subsequent drug use, with one exception: cocaine use in the cocaine study (RR=1.05, 95% CI 1.01-1.09). Overall, results do not indicate a causal relationship between noncontingent voucher receipt and increased drug use. Studies of the relationship between methadone enantiomer concentrations in plasma and saliva and of the relationship between methadone concentrations in these biologicalical matrices and treatment outcome are underway.